Fullerene film on metal surface: Diffusion of metal atoms and interface model

Abstract

We try to understand the fact that fullerene film behaves as n-type semiconductor in electronic devices and establish a model describing the energy level alignment at fullerene/metal interfaces. The C60/Ag(100) system was taken as a prototype and studied with photoemission measurements. The photoemission spectra revealed that the Ag atoms of the substrate diffused far into C60 film and donated electrons to the molecules. So the C60 film became n-type semiconductor with the Ag atoms acting as dopants. The C60/Ag(100) interface should be understood as two sub-interfaces on both sides of the molecular layer directly contacting with the substrate. One sub-interface is Fermi level alignment, and the other is vacuum level alignment.

Optical and Electronic Losses Arising from Physically Mixed Interfacial Layers in Perovskite Solar Cells

“…11 In addition, higher temperature facilitates Ag diffusion in C 60 . 10 These studies coupled with the fact that C 60 , BCP, and Ag are deposited by thermal evaporation in this study indicates the possibility of Ag diffusion within the ETL materials to form the C 60 + BCP + Ag physically mixed layer. To avoid the formation of the C 60 + BCP + Ag physically mixed layer and improve device performance, Ag deposition techniques and conditions that lead to limited Ag diffusion should be considered.…”

“…It has been studied that Ag diffuses up to 20 nm in BCP and forms a Ag + BCP complex, in which case electron transport takes place through the Ag + BCP complex rather than through the intact bulk BCP layer in solar cells . In addition, higher temperature facilitates Ag diffusion in C 60 . These studies coupled with the fact that C 60 , BCP, and Ag are deposited by thermal evaporation in this study indicates the possibility of Ag diffusion within the ETL materials to form the C 60 + BCP + Ag physically mixed layer.…”

“…Studies have shown that reflection loss and parasitic absorption in the conduction and charge carrier transport layers are dominant factors of optical loss in perovskite solar cells. − Shockley–Read–Hall recombination due to unpassivated defects in the perovskite absorber layer and other nonradiative recombination at absorber surfaces and interfaces contribute to electronic loss in perovskite solar cells. − All the studies related to the optical and electronic losses in perovskite solar cells until now have only focused on the losses via structurally and optically continuous bulk component layers. The presence of surface roughness on a layer leads to physical mixing with overdeposited layers at interfaces that can result in further optical and electronic losses. , Silver (Ag) used as a back electrical contact in perovskite solar cells is known to diffuse and interact with carrier transport layers to form a physically mixed region of Ag and these carrier transport layers. − In addition, Ag also interacts with halide ions within the perovskite absorber layer . Similarly, perovskite films deposited by spin-coating methods are reported to form a lower-density layer with larger perovskite grains and lower surface coverage near the substrate. − In perovskite solar cells, the optical and electronic losses arising from physical mixing between the component layers and their precise impact on device performance have not yet been reported.…”

Electronic structure evolution of single bilayer Bi(1 1 1) film on 3D topological insulator Bi2SexTe3−xsurfaces

“…Hetero-epitaxial film in atomic-scale structure had been investigated by SXRD and LEED analysis [39,40], and the inelastic-mean-free-path of the Bi 4f 7/2 photoelectron at kinetic energy 338 eV was estimated to be ~9 Å [41]. With these initial conditions a series of photoelectron attenuation values for the two chemical environments can be estimated using the peaks' intensity and then eventually the Bi coverage can be obtained [42]. Specifically, when the two peaks have nearly equal intensity the deposited Bi reaches a single bilayer, which is also cross-checked by the quartz microbalance flux monitor.…”

Field emission microscope for a single fullerene molecule

“…It should be also mentioned that the molecule layer was more rmly bonded to the surface than the molecules above the rst layer, as we will discuss later. The molecules above the rst layer are considered to be chemically pristine fullerenes (though, when the applied eld is present, they may be partially charged and/or have a dipole moment) because previous studies have revealed that the electronic properties of molecules above the rst layer are the same as that of the pristine C 60 , which was true for various metal substrates, including tungsten [18][19][20]. Hence, we call the rst layer a buffer layer to distinguish it from the other layers.…”